The
internal incisors are larger than the external pair, in the upper jaw,
smaller than the external pair, in the lower jaw. The crowns of the
upper molars exhibit four cusps, or blunt-pointed elevations, and a
ridge crosses the crown obliquely, from the inner, anterior cusp to the
outer, posterior cusp (Fig. 17 m2). The anterior lower molars have
five cusps, three external and two internal. The premolars have two
cusps, one internal and one external, of which the outer is the higher.
In all these respects the dentition of the Gorilla may be described in
the same terms as that of Man; but in other matters it exhibits many
and important differences (Fig. 17).
Thus the teeth of man constitute a regular and even series--without any
break and without any marked projection of one tooth above the level of
the rest; a peculiarity which, as Cuvier long ago showed, is shared by
no other mammal save one--as different a creature from man as can well
be imagined--namely, the long extinct 'Anoplotherium'. The teeth of the
Gorilla, on the contrary, exhibit a break, or interval, termed the
'diastema', in both jaws: in front of the eye-tooth, or between it and
the outer incisor, in the upper jaw; behind the eyetooth, or between it
and the front false molar, in the lower jaw.
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